Key Point: Grab your 9 iron for this shot. I find it works better to drive the ball up and out.
This is an awkward shot, so set yourself as best you can for stability. If your feet are not level, be sure to set yourself parallel to the slope. Similar to an uphill lie set up. Grip down on the shaft with a square clubface at address.
Make a three-quarter backswing with lots of wrist hinge. Grip pressure is light to promote a tension-free swing. Be sure to accelerate through the shot. The keys with this shot are lots of sand, zero tension, and good acceleration. On your follow-through, the clubface remains open; producing that high, soft shot.
Drive the clubhead down into the sand, just behind the ball. There will be no follow-through with this shot. Instead, you are hitting into the lip. Your ball should pop up and out.